The positions of the lines seen in an electron channeling pattern depend on the type and orientation of the crystal producing the pattern and on the energy of the incident electron beam. It is possible to make three lines intersect at a point by altering the energy or equivalently the wavelength, &lgr;, of the incident electrons. A mathematical expression, valid for all crystal classes, is derived for this wavelength in terms of the Miller indices and plane spacings of the Bragg planes which give rise to the three lines in question. The theory has been tested by using the hexagonal layer material NbSe2. The channeling lines whose Bragg planes are (22.0), (3¯0.0), and (22¯.2¯) were found to intersect at &lgr;=0.0098 nm which leads to acspacing ofc=1.26±0.01 nm. The x‐ray value is 1.254 nm. The analysis is formulated so that it can be used on a computer without graphics facilities.